EPDM elastomers, which are cured by the conventional sulfur vulcanization process, possess many very attractive durability properties. Outstanding among these are a high resistance to heat and a resistance to degradation by either oxygen or ozone. Two short-comings which have limited the use of this material are the relatively long cure time and, in particular, a relatively poor resistance to oil at elevated temperatures; these drawbacks have prevented this material from being used in seal applications such as those found in automotive transmissions and differentials. Often, neoprene is the only acceptable material for these applications and occasional supply problems have generated an interest in developing substitute materials.